Hydraulic control arrangement for a roof support unit of a mineral mining installation
US4440522A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 19, 1980 |
| Grant date | Apr 3, 1984 |
| Priority date | — |
| Expiry date | Dec 19, 2000 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21D23/08
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A roof support unit for a longwall mineral mining installation has a roof shield supported above a floor sill. A first hydraulic ram is provided for advancing the roof support unit. The roof shield is provided with a forward extension which is advanceable by means of a second hydraulic advance ram. A hydraulic control arrangement, which includes the two hydraulic advance rams is provided for controlling the advance of the roof shield extension in dependence upon the working stroke of the first hydraulic advance ram. The control arrangement is such that the amount of hydraulic fluid supplied to one of the pressure chambers of the second hydraulic advance ram is dependent upon the amount of hydraulic fluid expelled from one of the pressure chambers of the first hydraulic advance ram during the working stroke of the first hydraulic advance ram.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.